In the wireless communication technology, when a base station side (e.g., evolved node B, i.e., eNB) transmits data using a plurality of antennas, it can adopt a way of spatial multiplexing to improve a data transmission rate, that is, a transmitting end transmits different data at different antenna positions but using the same time frequency resources, and a receiving end (such as a user equipment, UE) also uses the plurality of antennas to receive the data. With a single user, resources of all the antennas are allocated to the same user, that user occupies independently physical resources allocated by the base station side within one transmission interval, and this kind of transmission mode is called as Single User Multiple-Input Multiple-Out-put (abbreviated as SU-MIMO); with multiple users, the space resources of various antennas are allocated to different users, one user shares the physical resources allocated by the base station side with at least one other user within one transmission interval, and the share way can be a space division multiple access way or a space division multiplexing way, and this kind of transmission mode is called as Multiple User Multiple-Input Multiple-Out-put (abbreviated as MU-MIMO); wherein, the physical resources allocated by the base station side refer to the time frequency resources. If a transmission system supports the SU-MIMO and the MU-MIMO at the same time, then the eNB needs to provide data under these two kinds of modes for the UE. When the UE is in the SU-MIMO mode or the MU-MIMO mode, it needs to know a Rank used by the eNB to transmit the MIMO data to that UE. In the SU-MIMO mode, the resources of all the antennas are allocated to the same user, the number of layers used for transmitting the MIMO data is just equal to the rank used by the eNB transmitting the MIMO data; correspondingly, in the MU-MIMO mode, the number of layers used by one user for transmission is less than the total number of layers for the eNB transmitting the MIMO data; and if switching between the SU-MIMO mode and the MU-MIMO is required to be performed, the eNB needs to notify the UE of different control data under different transmission modes.
In a Long Term Evolution (LTE) system, control signalings required to be transmitted in an uplink includes: Acknowledgement/Negative Acknowledgement (ACK/NACK) message, and three formats of information reflecting Channel State Information (CSI) of an downlink physical shared channel: channels quality indication (CQI), pre-coding matrix indicator (PMI) and rank indicator (RI).
In the LTE system, the ACK/NACK message is transmitted on a Physical Uplink Control Channel (PUCCH) by a format of 1/1a/1b (PUCCH format1/1a/1b); if the terminal (User Equipment, UE) needs to send the uplink data, then the data is transmitted on a Physical Uplink Shared Channel (PUSCH); the feedback of the CQI/PMI, the RI can be a periodic feedback, or can be a non-periodic feedback, and the specific feedback is shown in Table 1:
TABLE 1Uplink physical channel corresponding to the periodic feedbackand the non-periodic feedbackPeriodic CQINon-periodic CQI reportScheduling modereport channelchannelFrequency non-selectivityPUCCHFrequency selectivityPUCCHPUSCH
Wherein, as to the CQI/PMI, RI of the periodic feedback, if the UE does not need to send the uplink data, then the CQI/PMI, RI of the periodic feedback are transmitted on the PUCCH by a format of 2/2a/2b (PUCCH format2/2a/2b), and if the UE needs to send the uplink data, then the CQI/PMI, RI are transmitted on the PUSCH; as to the CQI/PMI, RI of the non-periodic feedback, they are only transmitted on the PUSCH.
The long term evolution Release 8 standard defines the following three kinds of downlink physical control channels: Physical Control Format Indicator Channel (abbreviated as PCFICH), Physical Hybrid Automatic Retransmission Request Indicator Channel (abbreviated as PHICH) and Physical Downlink Control Channel (abbreviated as PDCCH). The PDCCH is used for carrying Downlink Control Information (abbreviated as DCI), including: uplink and downlink scheduling information, and uplink power control information. The DCI format is divided into the following types: DCI format 0, DCI format 1, DCI format 1A, DCI format 1B, DCI format 1C, DCI format 1D, DCI format 2, DCI format 2A, DCI format 3 and DCI format 3A, etc.; wherein, the transmission mode 5 supporting the MU-MIMO utilizes the downlink control information of the DCI format 1D, and a Downlink power offset field δpower-offset in the DCI format 1D is used for indicating the information of reducing power of one user by half in the MU-MIMO mode (that is, −10 log 10(2)). Because the transmission mode 5 of the MU-MIMO only supports the MU-MIMO transmission of two users, through this downlink power offset field, the transmission mode 5 of the MU-MIMO can support the dynamic switching between the SU-MIMO mode and the MU-MIMO mode; but the DCI format only supports transmission of one stream for one UE regardless of in the SU-MIMO mode or the MU-MIMO mode. The LTE Release 8 supports the single user transmission of two streams at most in a transmission mode 4, but, because the switching between the transmission modes can only be semi-static, it cannot perform the dynamic switching between the single user multi-stream transmission and the multi-user transmission in the LTE Release 8.
In an LTE Release 9, in order to enhance the downlink multi-antenna transmission, a transmission mode of the dual streams beamforming is introduced, which is defined as a transmission mode 98, and the downlink control information adds a DCI format 2B to support that transmission mode. There is an identification bit of a scrambling identity (abbreviated as SCID) in the DCI format 2B to support two different scrambling sequences. The eNB can allocate the two scrambling sequences to different users, to multiplex a plurality of users in the same resource. In addition, when only one transmission block is enabled, a new data indication (NDI) bit corresponding to a disabled transmission block is also used to indicate an antenna port when transmitting by single-layer.
In addition, in an LTE Release 10 (Release 10), in order to further enhance the downlink multi-antenna transmission, a transmission mode of a new closed-loop space multiplexing is added, which is defined as a transmission mode 9. This kind of transmission mode not only can support the single user MIMO, but also can support the multi-user MIMO, and moreover can support the dynamic switching between both of them. In addition, this kind of transmission mode supports transmission of 8 antenna ports also. Such new transmission mode has already determined to use a Demodulation Reference Signal (abbreviated as DMRS) as a pilot frequency for demodulating, and the UE needs to obtain a position of the pilot frequency, then it can make estimation of channels and interference on the pilot frequency. Different total numbers of the transmission layers have different pilot frequency patterns, for example, there are three kinds of different DMRS patterns in the LTE Release 10 preliminarily; specifically, when the total number of the transmission layers or the rank is 1 or 2, the first pattern (DMRS pattern 1) is used; when the total number of the transmission layers or the rank is 3 or 4, the second pattern (DMRS pattern 2) is used, when the total number of the transmission layers or the rank is any value of 5 to 8, the third pattern (DMRS pattern 3) is used. In the SU-MIMO mode, the data in all transmission layers are sent to the same UE, so as long as the UE obtains the rank, it can acquire the pattern of the pilot frequency and also can acquire the position of the pilot frequency. In the SU-MIMO mode, the UE needs to acquire the rank and the number of the layers for performing transmission to the UE at the beginning, and also the UE needs to acquire the pilot frequency pattern for transmission, then it can obtain the position of the pilot frequency of the interference. In addition, different DMRS ports use different spectrum spreading codes, and the UE also needs to acquire the spectrum spreading code used for transmission, thus it can obtain messages on the pilot frequency.
In the R10, the UE, through high level signaling, is semi-statically configured to receive data transmission of the Physical Downlink Shared Channel (PDSCH) according to an indication of PDCCH in a UE-Specific search space and based on one of the following transmission modes:
mode 1: Single-antenna port; port 0;
mode 2: Transmit diversity;
mode 3: Open-loop spatial multiplexing;
mode 4: Closed-loop spatial multiplexing;
mode 5: Multi-user MIMO;
mode 6: Closed-loop Rank=1 pre-coding;
mode 7: Single-antenna port; port 5;
mode 8: Dual layer transmission, that is, dual streams beamforming;
mode 9: space multiplexing of at most 8 layers.
In the R10, as to the feedback of the physical uplink control channel PUCCH, the transmission mode 9 supports the feedback mode of mode 1-1 and mode 2-1. As to the feedback mode of mode 1-1 of the transmission mode 9, it further includes a sub-mode 1 and a sub-mode 2 which are distinguished through the high layer configuration signaling PUCCH_format1-1_CSI_reporting_mode. As to the feedback of the physical uplink shared channel PUSCH, the transmission mode 9 needs to support three kinds of feedback modes, which are mode 1-2, mode 2-2 and mode 3-1 respectively.
In the R10, it newly adds the transmission mode 9 and the Channel-State Information-Reference Symbol (CSI-RS). The transmission mode 9 performs the channel measurement based on the CSI-RS, thus calculates and obtains the CQI. The other transmission modes perform the channel measurement based on the CRS, thus calculate the CQI. In the R10, it correspondingly adds some CSI-RS parameters to indicate its attributes also. Compared with the CRS in R8, some parameters are similar, and some parameters are newly added. For example, for the number of CSI-RS ports, it is similar with the number of CRS ports in R8, but a sub-frame configuration periodic parameter of the CSI-RS is newly added. The following parameters are cell-specific and configured by the high layer signaling, and are used for the definition of the CSI-RS, and the parameters include: the number of CSI-RS ports, CSI-RS configuration, CSI-RS sub-frame configuration parameter ICSI-RS, sub-frame configuration periodic TCSI-RS, the sub-frame offset and UE assumption on reference PDSCH transmitted power for CSI feedback Pc 
In the R10, as to the transmission mode 9, a new concept of “dual-codebook” or “double PMI” is introduced, so two PMIs need to be fed back; as to 8 antennas, the first PMI indicates the channel state information of broadband, and the second PMI indicates the channel state information of sub-band; the whole pre-coding matrix information can be get only by obtaining two PMIs, wherein, the sub-band includes the situation of the broadband; as to 2 antennas and 4 antennas, what the first PMI indicates is a unit matrix, and the second PMI is equivalent to the PMI in the original R8 protocol.
As to the new transmission mode 9 of the R10 protocol, there is still not an effective method for distinguishing whether there is a PMI/RI feedback or no PMI/RI feedback, and this defect will cause that the transmission mode 9 is unable to support quick switching between the two feedback mode types, thereby resulting in the transmission mode 9 is unable to support the single layer transmission in a frequency division duplex (FDD) mode, and is unable to use the reciprocity of channels in a time division duplex (TDD) mode, which will reduce the system flexibility and performance.